Conventionally, in the field of blood drawing, a blood component such as platelets is collected by collecting only the component from drawn blood and returning the remaining blood components into the donor. In such operation, a blood component separation device including a centrifugal separator is used.
In recent years, in the field of radiation therapy of cancer or the like, transfusion of platelets is widely performed, and high-concentration platelet liquid is necessary. To obtain high-concentration platelet liquid, Patent Literature 1 discloses an art using a blood component separation device to temporarily store low-concentration platelet liquid in a buffy coat bag and store only high-concentration platelet liquid in a platelet intermediate bag.
In this operation, low-concentration platelet liquid flows out first from the centrifugal separator, then high-concentration platelet liquid, and finally low-concentration platelet liquid again. When the first portion and the last portion of the platelet liquid, which has low-concentration of platelets, are stored in the platelet intermediate bag, the concentration of the platelet liquid stored in the platelet intermediate bag will naturally be reduced.
To avoid such reduction in concentration, the low-concentration platelet liquid, that is, the first portion and the last portion of the platelet liquid, is temporarily stored in the buffy coat bag. In the second cycle, the stored platelet liquid is mixed with the whole blood drawn from a donor and supplied to the centrifugal separator. By repeating this process, only high-concentration platelet liquid can be stored in the platelet intermediate bag.